This section illustrates useful background information without admission of any technique described herein representative of the state of the art.
Graphene field effect transistors (GFET) functioning as phototransistors, are used in imaging sensor applications. They have a very high charge carrier mobility, but previously it has been impossible to provide a feasible sensor, and especially large area sensor array, architecture since it is has been difficult to enable temporary signal storage due to the continuously flowing current of the GFET.
Previously GFETs have been used in imaging sensor by changing the current into voltage using integrating transimpedance amplifiers and storing integrated charge in a sample and hold capacitor after the amplifier. Such an arrangement requires the amplifier arrangement for each pixel, i.e. each GFET, separately increasing cost and power requirements, especially in large area sensor arrays, such as used for example in x-ray imaging.